U.S. patent number 4,421,464 [Application Number 06/139,695] was granted by the patent office on 1983-12-20 for liquid helium pump.
This patent grant is currently assigned to Kernforschungszentrum Karlsruhe Gesellschaft mit beschrankter Haftung. Invention is credited to Klaus Jentzsch, Kurt Schmidt.
United States Patent |
4,421,464 |
Schmidt , et al. |
December 20, 1983 |
Liquid helium pump
Abstract
A pump for driving a liquid, particularly liquid helium, has an
electromatic drive contained in its entirety in the pump housing
for generating an axially oriented force to reciprocate the pumping
member. The electromagnetic drive has a stationary electromagnet
supported in the pump housing and including an annular air gap and
an energizing solenoid for generating a magnetic flux in the air
gap. The electromagnetic drive further has a coil carrier attached
to the pumping member to move therewith as a unit; the coil carrier
has a travelling path passing through the air gap and being
parallel to the pump axis. Further, a moving coil is mounted on the
coil carrier for traversing the magnetic flux in the air gap,
whereby an electromagnetic force parallel to the pump axis is
exerted on the moving coil for displacing the moving coil, the coil
carrier and the pumping member as a unit.
Inventors: |
Schmidt; Kurt
(Karlsruhe-Waldstadt, DE), Jentzsch; Klaus
(Stutensee, DE) |
Assignee: |
Kernforschungszentrum Karlsruhe
Gesellschaft mit beschrankter Haftung (Karlsruhe,
DE)
|
Family
ID: |
6068334 |
Appl.
No.: |
06/139,695 |
Filed: |
April 11, 1980 |
Foreign Application Priority Data
|
|
|
|
|
Apr 14, 1979 [DE] |
|
|
2915199 |
|
Current U.S.
Class: |
417/412; 417/417;
417/472; 310/27; 417/418; 505/910 |
Current CPC
Class: |
H02K
55/00 (20130101); F04B 17/042 (20130101); F04B
15/08 (20130101); H02K 33/18 (20130101); Y02E
40/60 (20130101); Y02E 40/62 (20130101); Y10S
505/91 (20130101) |
Current International
Class: |
F04B
15/08 (20060101); F04B 17/03 (20060101); F04B
15/00 (20060101); H02K 33/18 (20060101); F04B
17/04 (20060101); H02K 55/00 (20060101); F04B
017/04 (); F04B 045/02 () |
Field of
Search: |
;417/412,413,472,473,417,418 ;310/27,10 ;92/44 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gluck; Richard E.
Assistant Examiner: Cuomo; Peter M.
Attorney, Agent or Firm: Spencer & Frank
Claims
What is claimed is:
1. In a pump for driving liquid helium, including a pump housing
having means defining a pump inlet and a pump outlet; a pumping
member arranged in the housing for reciprocating motion parallel to
a pump axis for drawing liquid helium into the pump through the
pump inlet and driving liquid helium out of the pump through the
pump outlet; and an electromagnetic drive means contained in its
entirety in the pump housing for generating an axially oriented
force applied to the pumping member to reciprocate the same; the
improvement wherein said electromagnetic drive means comprises:
(a) a stationary electromagnet supported in said pump housing and
including
(1) non-magnetic first and second coil carriers fixedly supported
in said pump housing and surrounding said axis; said second coil
carrier coaxially surrounding said first coil carrier and defining
therewith an annular clearance constituting an air gap surrounding
said axis and having a length dimension parallel to said axis;
(2) first, second, third and fourth superconductive energizing
solenoids carrying an energizing current to generate a magnetic
flux in said air gap; said first and second energizing solenoids
being mounted in an axially spaced relationship on said first coil
carrier; said third and fourth energizing solenoids being mounted
in an axially spaced relationship on said second coil carrier; said
first energizing solenoid being in radial alignment with said third
energizing solenoid and said second energizing solenoid being in
radial alignment with said fourth energizing solenoid;
(b) a non-magnetic third coil carrier attached to said pumping
member to move therewith as unit; said third coil carrier
surrounding said axis and having a travelling path passing through
said air gap and being parallel to said axis;
(c) a superconductive cylindrical moving coil carrying a control
current and being mounted on said third coil carrier coaxially with
said first, second, third and fourth energizing solenoids for
traversing the magnetic flux in said air gap whereby an
electromagnetic force parallel to said axis is exerted on said
moving coil for displacing said moving coil, said third coil
carrier and said pumping member as a unit; said moving coil having
an axial length which is at least approximately equal to the axial
distance between said first and second energizing solenoids;
and
(d) means for supplying first, second, third and fourth energizing
solenoids and said moving coil with said energizing current and
said control current, respectively.
2. A pump as defined in claim 1, wherein said pumping member is a
hollow piston surrounding said electromagnetic drive means; further
comprising a guide rod stationarily supported in said pump housing
and extending into said hollow piston in a coaxial relationship
therewith; further wherein said guide rod terminates in a free
tubular portion having an axially parallel slot; further comprising
a web affixed to said third coil carrier and extending into said
slot for being linearly guided by said slot to prevent rotation of
said first coil carrier about said axis.
3. A pump as defined in claim 1, wherein said pumping member is a
hollow piston surrounding said electromagnetic drive means, further
wherein said second coil carrier is sleeve-shaped and has a base;
the improvement further comprising means defining ports in said
second coil carrier in the zone of said base and in said first coil
carrier in the zone of said air gap; said ports providing a flow
path between said pump inlet and said pump outlet; said cylindrical
moving coil and said energizing solenoids being arranged in said
flow path for exposure to the liquid helium driven by the pump.
4. A pump as defined in claim 1, wherein said first coil carrier is
tubular and said second coil carrier is pot-shaped; said first coil
carrier being affixed to said second coil carrier in the interior
thereof and in a coaxial relationship therewith.
5. A pump as defined in claim 4, wherein said first, second and
third coil carriers each have an outer face; the improvement
further comprising means defining in said outer face separate
annular grooves constituting winding spaces for accommodating,
respectively, said first and second energizing solenoids, said
third and fourth energizing solenoids and said moving coil.
6. A pump as defined in claim 1, wherein said pumping member is a
bellows having a fixed end and a movable end; further wherein said
electromagnetic drive means is accommodated in a space enclosed by
said bellows; further comprising a support fixedly held by said
pump housing and extending axially into the space surrounded by
said bellows; said third coil carrier being affixed to said movble
end of said bellows; said first coil carrier being sleeve-shaped
and having a centrally located septum extending transversely to
said axis; said first coil carrier being affixed to said support at
said septum; said second coil carrier being pot-shaped and being
mounted on said support.
7. A pump as defined in claim 6, further comprising means defining
ports in said septum and in said pot-shaped second coil carrier for
providing a flow path between said pump inlet and said pump
outlet.
8. A pump as defined in claim 7, wherein said third coil carrier is
sleeve-shaped and has a terminus projecting beyond said air gap;
further comprising a closure plate affixed to said movable end of
said bellows for closing off the space surrounded by said bellows;
said third coil carrier being attached to said closure plate at
said terminus of said third coil carrier.
9. A pump as defined in claim 8, further comprising a ring
surrounding said closure plate; said ring being affixed to said
closure plate and to said movable end of said bellows for mounting
said closure plate on said bellows.
Description
BACKGROUND OF THE INVENTION
This invention relates to a pump; more particularly, to a liquid
helium pump having a superconductive electromagnetic drive which
includes a stationary superconductive energizing solenoid connected
to the pump housing and a superconductive element which is movable
by means of the field generated by the energizing solenoid and
which is fixedly attached to the pumping member proper of the
pump.
Pumps of the above-outlined type are needed for driving liquid or
supercritical helium in a closed circuit or, in general, for
displacing liquid helium.
Particularly in the field of fusion technology, the use and
operation of coreless fusion magnets are indispensable. The coils
of the fusion magnets--which generate magnetic fields of a flux
density in the order of a few Tesla--are constituted by hollow
superconductors, which may have a length up to 1,000 m and which
are to be cooled with helium which is in a single phase. The
displacement of the helium is effected at a pressure above 2.4 bar
and at a temperature of approximately 4.2 K. The pressure
difference between inlet and outlet is in the order of magnitude of
1 bar. In particular modes of application, such as in installations
for testing superconductive hollow conductors as a function of the
parameters of the flowing helium, such as pressure and flow
quantity, there is further required a constant capacity and a
constant pressure difference during the pump cycle. These
requirements are not met by known piston pumps driven by an
eccentric.
In an article entitled "A Reciprocating Liquid Helium Pump Used for
Forced Flow of Supercritical Helium" by G. Krafft et al
(Cryogenics, February 1978), there is disclosed a piston pump for
driving liquid helium. The pump drive is arranged externally of the
cryostat and therefore the piston rod has to pass through the
cryostat wall. Such an arrangement requires a vacuumtight and
heliumtight seal and is involved with substantial expense. These
difficulties are circumvented in another known liquid helium pump
described in an article entitled "Heat Transfer by the Circulation
of Supercritical Helium" by H. H. Kolm et al (Advances in Cryogenic
Engineering, Volume 11, Plenum Press, New York, 1965). In this
arrangement, the ferromagnetic piston is, with bellows,
accommodated in a pump housing and a solenoid for driving the
piston is arranged externally of the pump housing. The pump housing
which necessarily is made of a non-magnetic material, on the one
hand, increases the gap between the solenoid and the piston and, on
the other hand, it does not eliminate undesired effects of foreign
(external) magnetic fields. It is another disadvantage of this type
of pump that it has only a small output of approximately 6.4
cm.sup.3 /s.
In an article entitled "An Electrically Pumped Liquid Helium
Transfer System" by B. Darrel et al (Advances in Cryogenic
Engineering, Volume 11, Plenum Press, New York, 1965), there is
disclosed a liquid helium pump wherein the superconductive driving
coil is a disc coil mounted at an end of a bellows-equipped
superconductive piston received in the pump housing. The piston is
moved by the driving coil by attraction and repulsion. The forces
exerted on the piston change substantially during each stroke,
because as the distance between the piston and the driving coil
increases, the forces exerted on the piston drop sharply. Further,
in this type of pump too, strong foreign magnetic fields may
significantly interfere with the pumping operation. The output of
this pump too, is low; it is only approximately 7 cm.sup.3 /s.
In the Handbuch fur Hochfrequenz- und Elektrotechniker, (Manual for
the High Frequency Technician and Electrotechnician), Volume 1 3rd
Edition (published by Verlag fur Radio- Foto- Kinotechnik Berlin,
1952), on pages 438 and 439 there is described a drive system for
an electromagnetic loudspeaker. The drive system comprises a
pot-shaped electromagnet having a central core which carries an
energizing solenoid and the free end of which forms, with a
disc-shaped pole shoe, an annular gap into which swings the voice
coil for moving the loudspeaker diaphragm when the voice coil is
excited with a voltage in the sound frequency range.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved pump,
particularly a liquid helium pump whose superconductive driving
arrangement is free from structural components passing through the
pump housing; further, which is capable of an interference-free
operation even in strong foreign magnetic fields of a flux of
several Tesla and which, at a given appropriate capacity has a
constant differential pressure between the pump inlet and the pump
outlet and thus has a constant flow rate.
This object and others to become apparent as the specification
progresses, are achieved by the invention, according to which,
briefly stated, the pump has an electromagnetic drive contained in
its entirety in the pump housing for generating an axially oriented
force to reciprocate the pumping member. The electromagnetic drive
has a stationary electromagnet supported in the pump housing and
including an annular air gap and an energizing solenoid for
generating a magnetic flux in the air gap. The electromagnetic
drive further has a coil carrier attached to the pumping member to
move therewith as a unit; the coil carrier has a travelling path
passing through the air gap and being parallel to the pump axis.
Further, a moving coil is mounted on the coil carrier for
traversing the magnetic flux in the air gap, whereby an
electromagnetic force parallel to the pump axis is exerted on the
moving coil for displacing the moving coil, the coil carrier and
the pumping member as a unit.
The advantages of the invention reside particularly in that by
simple means a compact liquid helium pump is provided which has a
large capacity, a constant flow rate and which operates reliably
even in strong foreign magnetic fields.
BRIEF DESCRIPTION OF THE DRAWING
FIGS. 1 through 4 are schematic axial sectional views of four
preferred embodiments of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to FIG. 1, there is shown, in axial section, a piston
pump having an electromagnetically driven double-acting piston 1
arranged in a pump housing 2. The base 3 of a sleeve-like coil
carrier 4 is attached to a central septum 5 of the piston 1 by a
screw connection 6. The coil carrier 4 has, at its outer surface, a
depression constituting a winding space 7 which accommodates a
superconductive moving coil 8. An electromagnet 9 comprising a
cylindrical ferromagnetic core 10 and a pot-like yoke 11
surrounding the core 10 is arranged within the pump housing 2 and
is attached fixedly thereto in a coaxial relationship with the coil
carrier 4. The yoke 11 forms an annular gap 13 with the free end 12
of the core 10. The lateral outer face of core 10 has a depression
constituting an annular winding space 14 which receives a
superconductive energizing solenoid 15 arranged coaxially with the
moving coil 8. In the annular gap 13 the current flowing in the
energizing solenoid 15 generates a radial magnetic field whose
field lines are, at every location of the annular gap 13,
perpendicular to the current flowing in the moving coil 8. As a
result, a force 17 which is parallel to the axis 16 of the piston 1
and the direction of which is determined exclusively by the
direction of the control current, is exerted on the moving coil 8
and thus, with the intermediary of the coil carrier 4, on the
piston 1. The superconductive electromagnetic drive of the piston 1
is arranged in one of its two piston chambers 18 and 19 separated
by the septum 5 and is cooled by the helium flow generated by the
operation of the pump.
In case of constant flux in the annular gap 13, the force 17
exerted on the piston 1 is proportionate to the control current
flowing in the moving coil 8. In case of constant control current,
the force 17 is constant during each stroke and thus the pressure
difference generated by the pump is also constant. Only upon
reaching either dead center of the piston 1 does the pressure
difference drop to zero for a period of approximately 10 ms. As the
piston 1 reaches either of its two dead centers, a respective
movable contact 20 carried by the piston 1 engages a stationary
contact 20a mounted on the yoke 11, whereby a circuit of a control
device 21 is closed, resulting in a reversal of the direction of
the control current in the moving coil 8.
A predetermined pressure difference can be set by an appropriate
choice of the control current intensity.
The coil carrier 4, similarly to the pump housing 2 and the piston
1, is made of a non-magnetic material such as brass or stainless
steel.
If the magnet 9 is, while maintaining the annular gap 13 free,
surrounded at all sides by a superconductive shield 22, for
example, of Nb.sub.3 Sn, the pump can be operated interference-free
even in a strong external magnetic field having a magnetic flux
density of several Tesla. The pump housing 2 is closed at opposite
ends by closures 23 flanged thereto; in each closure 23 there is
provided a spherical inlet check valve 24 and a spherical outlet
check valve 25. As the piston 1 reciprocates in response to the
driving effect of the force 17, liquid helium is alternatingly
drawn through the respective inlet check valves 24 from supply
conduits 26 and 27 and is alternatingly driven through the
respective outlet check valve 25 into pressure conduits 28 and
29.
The magnetic flux in the annular gap 13 is approximately B=2 Tesla
(iron saturation) for a pump with the following
characteristics:
diameter of piston 1=60 mm;
stroke of piston 1=15 mm;
inner diameter of moving coil 8=25 mm;
length of moving coil 8=22 mm;
the winding of the moving coil 8 has a thickness of 1 mm; it is in
three layers with 66 turns each;
width of air gap 13=2 mm;
height of air gap 13=5 mm;
the winding of the energizing solenoid 15 has two layers with 60
turns each;
the superconductor for both the moving coil 8 and the energizing
solenoid 15 is a copper-stabilized NbTi-multifilament wire of 0.3
mm diameter.
With a current J=20 A in the moving coil 8 and a conductor length
L=3.5 m in the annular gap 13, the piston 1 is exposed to an axial
force F=J.times.B.times.L=140 N and in case of a piston surface of
29 cm.sup.2, there is obtained a differential pressure of
.DELTA.p=0.5 bar. The pressure difference may be increased without
difficulty, since the assumed current of 20 A is far below the
critical current intensity of the superconductor. In case of a
frequency of 2.5 Hz, the capacity is 0.2 liter/sec.
The yoke 11 of the magnet 9 and the magnetic shield 22 have radial
ports 30 and the solenoid carrier 4 has, adjacent its bottom 3,
radial ports 31. During operation of the pump, a continuous helium
flow is maintained through the ports 30 and 31 in the zone of the
superconductive moving coil 8 and the superconductive energizing
coil 15.
Turning now to FIG. 2, there is shown in axial section a bellows
pump whose superconductive electromagnetic drive 3, 4, 7-16, 20, 21
and 22 is substantially identical to the electromagnetic drive
described in connection with the embodiment illustrated in FIG.
1.
The yoke 11 of the magnet 9 of the bellows pump shown in FIG. 2 is
connected with a support 40 which has a central bore 41 through
which passes a current supply cable 42 for the moving coil 8 and
the energizing solenoid 15. The pump has a pumping bellows 46 which
at its movable upper end (as viewed in FIG. 2) is affixed to a ring
45 to which there is coaxially welded a closure plate 44 mounted on
the base 3 of the coil carrier 4, for example, by means of a screw
connection. On the ring 45 there is supported a movable contact 20b
which cooperates, identically to the embodiment described in
connection with FIG. 1, alternatingly with the one and the other
stationary contact 20c supported in the pump housing 56. Each time
the bellows 46 reaches its compressed or expanded limit position,
the movable contact 20b engages the one or the other stationary
contact 20c and thus, with the intermediary of a conductor 43 also
passing through the bore 41 of the support 40, closes a circuit of
the control device 21 for reversing the control current flowing in
the moving coil 8 supported on the coil carrier 4.
The lower, fixed end of the bellows 46 is adjoined by a first valve
disc 47 which surrounds a foot 48 of the support 40. Between the
first valve disc 47 and a second valve disc 49 there is clamped a
low-temperature resistant plastic foil 50 constituting a valve
diaphragm. The valve diaphragm has non-illustrated tongues
(segments) which are actuated by the flowing helium and which thus
operate as flutter valves. The diaphragm tongues, dependent upon
the direction of the force 17 acting on the moving coil 8,
alternatingly open first valve ports 51, 51a provided in second
valve disc 49 for allowing inflow of helium from a supply conduit
57 and second valve ports 52, 52a provided in the first valve disc
47 and the foot 48 of the support 40 for driving the helium into
the outlet (pressure) conduit 62.
The support 40, the first valve disc 47 and the second valve disc
49 are, together with the valve diaphragm 50, affixed to a base
plate 54 by a screw connection 53 and are mounted, together with
the base plate 54 on the pump housing 56 by means of bolts 55.
Thus, the helium flows from the inlet conduit 57, through the valve
port 51 and an opening 58 in the valve disc 47 into the space 59
between the pump housing 56 and the bellows 46 and through the
valve port 51a and an opening 60 in the foot 48 of the support 40
into the space 61 surrounded by the bellows 46. The outlet pressure
conduit 62 communicates with the space 59 through valve port 52 and
an opening 63 in the valve plate 49 and further, the outlet conduit
62 communicates with the space 61 through the valve port 52a and an
opening 64 in the valve plate 49.
Turning now to the embodiment illustrated in FIG. 3, there is shown
a piston pump which is driven with the aid of an iron-free magnet
having an annular gap. In the pump housing 2 there is accommodated
a pot-shaped piston 70 in which there is fixedly attached a
sleeve-shaped coil carrier 71. The latter has, at its open end, an
annular groove-shaped winding space 72 for receiving a
superconductive moving coil 73.
To the upper housing closure 23 there is fixedly attached a
pot-shaped further coil carrier 74 which, at its outer face, has
two annular groove-shaped winding spaces 75 for receiving two
axially spaced energizing solenoids 76 and 77.
A further, tubular coil carrier 78 is inserted coaxially into the
coil carrier 74 and is connected with the latter in such a manner
that there is formed an annular gap 79, through which the coil
carrier 71 may travel. On the outside of the coil carrier 78 there
are provided two annular groove-shaped winding spaces 80 for
receiving respective, axially spaced energizing coils 81 and 82.
The axial distance between the energizing coils 76 and 77 and
between the energizing coils 81 and 82 corresponds approximately to
the axial length of the moving coil 73. The coil carriers 71, 74
and 78 are made of a non-magnetic, low-temperature resistant
material.
The coil carrier 74 has a base 85 (oriented towards the upper
housing closure 23 as viewed in FIG. 3) which is provided with
ports 84. The sleeve-shaped portion of the coil carrier 74 has
ports 83 located adjacent the base 85. Further, the coil carrier 78
has bores 86 in a zone adjacent the upper winding space 80, as
viewed in FIG. 3. The bores 86 establish communication between the
annular gap 79 and a space 87 which is defined by the piston 70 and
the base 85 of the coil carrier 74 and whose volume is variable by
the stroke of the piston 70.
In the center of the base 85 of the coil carrier 74 there is
coaxially arranged a guide rod 88 which projects into the space 87
and which has, at its tubular free end, a slot 89 which extends
parallel to the pump axis 16. The slot 89 guides a flat web 90
connected with the coil carrier 71, whereby rotations of the moving
coil 73 mounted on the coil carrier 71 cannot occur about the axis
16. In this manner it is ensured that the superconductive lead
wires 92 which are associated with the moving coil 73 and which
pass through an axial bore 91 of the guide rod 88 as well as the
tubular end portion thereof are not damaged by an undesired rotary
motion of the coil carrier 71. The guide rod 88 has, in its tubular
part, a radial bore 93 through which pass two further
superconductive wires 94 which are also accommodated in the axial
bore 91 of the guide rod 88 and which serve as lead wires for the
energizing solenoids 76, 77, 81 and 82.
The guide rod 88 and the flat web 90 may be a fiberglass-reinforced
plastic or a ceramic material, while the other structural elements
are made of a non-magnetic metallic material.
In the embodiment illustrated in FIG. 3, the annular gap magnet 9
of FIG. 1 is thus replaced by an arrangement which has four
superconductive iron-free energizing solenoids and wherein the
direction of the energizing current is the same in radially
adjacent energizing coils while it is opposed in axially adjacent
energizing coils. Under these conditions, the described solenoid
arrangement generates in its radial symmetry plane a radial
magnetic field which exerts on the moving coil a force that
corresponds to that derived from a magnet with an annular gap (such
as the magnet 9).
The principal data of a liquid helium pump provided with a drive
system in accordance with FIG. 3 may be as follows:
diameter of piston 70=60 mm;
stroke of piston 70=10 mm;
inner diameter of moving coil 73=45 mm;
axial length of moving coil 73=12 mm;
the winding of the moving coil 73 is in two layers with 36 turns
each; the wire is a copper-stabilized NbTi-multiplication wire
having a diameter of 0.3 mm;
the energizing solenoids 76, 77, 81 and 82 have a total of 420
turns of a superconductive wire having a diameter of 0.3 mm.
At a current of 50 A a radial magnetic field of B=0.25 to 0.4 Tesla
is generated at the location of the moving coil 73. The average
field affecting the moving coil 73 is, up to .+-.5 mm excursion,
constant within 3% and has a flux of 0.29 Tesla. The axial force
exerted on the piston 70 is F=150 N; the differential pressure is
.DELTA.p=0.5 bar. At a frequency of 3.5 Hz the capacity is 0.2
liter/sec.
A liquid helium pump equipped with the above-described drive
comprising four iron-free energizing coils and an iron-free moving
coil can also operate interference-free without a magnetic shield
in a homogeneous external magnetic field which is parallel to the
coil axis (piston axis 16) and which has a flux of several Tesla or
in a non-homogeneous magnetic field which is symmetrical to the
coal axis.
Turning now to the embodiment illustrated in FIG. 4, there is
shown, in longitudinal section, a bellows pump which is driven by
an arrangement which is described in connection with the FIG. 3 and
which thus has four iron-free energizing solenoids 76, 77, 81 and
82 as well as an iron-free moving coil 73. The pump housing 56, the
flange 54, the first valve disc 47, the second valve disc 49, the
valve diaphragm 50 and the screw connection 53 correspond to the
components described in connection with the embodiment illustrated
in FIG. 2. The same applies to the structure, the basic spatial
arrangement and the function of the iron-free energizing solenoids
76, 77, 81 and 82 and the iron-free moving coil 73. In this
embodiment, the energizing coils 81 and 82 are arranged in
respective annular groove-shaped winding spaces 80 provided in the
outer face of a coil carrier 100 which is of tubular configuration
and which has in its central transverse plane an apertured septum
101. The energizing coils 76 and 77 are accommodated in annular
groove-shaped winding spaces 75 provided in the outer face of a
pot-shaped coil carrier 102. The latter is inserted on a support
103 and is held by the coil carrier 100 attached to the end of the
support 103 by means of a screw connection 104. The coil carriers
100 and 102 are centered to be in alignment with the common axis 16
and together define an annular gap in which reciprocates a coil
carrier 105 arranged coaxially with the annular gap. In the outer
face of the coil carrier 105 there is provided an annular
groove-shaped winding space 72 for accommodating the moving coil
73.
The coil carrier 105 is, at its upper end, attached to the closure
plate 44 which, in turn, is secured to the upper end of the bellows
46 by means of the ring 45. The other, lower end of the bellows 46
is welded to the first valve disc 47.
The base of the coil carrier 102 has openings 106 and the septum
101 of the coil carrier 100 has openings 107 through which liquid
helium may flow during the operation of the pump. A plurality of
bores 108 along the radius of the annular gap between the coil
carriers 100 and 102 ensures a cooling of the energizing coils and
the moving coil.
It will be understood that the above description of the present
invention is susceptible to various modifications, changes and
adaptations, and the same are intended to be comprehended within
the meaning and range of equivalents of the appended claims.
* * * * *